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- Otto Posterman
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Pickering's Triangle in the Veil
Explanation: Chaotic in appearance, these filaments
of shocked, glowing gas break across planet Earth's sky toward the constellation of Cygnus, as part of the Veil Nebula
. The Veil Nebula itself is a large supernova remnant
, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Blasted out in the cataclysmic event, the interstellar shock waves plow through space sweeping up and exciting interstellar material. The glowing filaments are really more like long ripples in a sheet seen almost edge on, remarkably well separated into the glow of ionized hydrogen and sulfur atoms shown in red and green, and oxygen in blue hues. Also known as the Cygnus Loop, the Veil Nebula now spans
nearly 3 degrees or about 6 times the diameter of the full Moon. While that translates to over 70 light-years at its estimated distance of 1,500 light-years, this field of view spans less than one third that distance. Identified as Pickering's Triangle for a director of Harvard College Observatory and cataloged as NGC 6979, the complex of filaments might be more appropriately known as Williamina Fleming's Triangular Wisp
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Very interesting image.
A special structure
The Veil is one of my favorite visual targets. Using a UHC or OIII filter one can see incredible fine structure in the brighter main segments, as well as lots of debris (like Pickering's Triangle) between them. It's angular size is so large that one must pan the scope around a lot to take it all in. Under very dark skies, I have even seen the main larger arc with 11x70 binoculars.
- Stellar Cartographer
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Nice to see this part of the Veil Nebula get some attention! Pickering's Triangle was discovered by Williamina Fleming and she named it in honour of Edward Pickering. Williamina Fleming is one of my favourite astronomers and if I could use a time machine to visit an astronomer, it would be her. Some of her other discoveries include the very well known Horsehead Nebula
(later catalogued by Edward Emerson Barnard) and the obscure planetary nebula Fg 1
Also there is a nice image of the whole Veil Nebula by Sara Wager
, somewhere in there is a planetary nebula!
The notion of seeing a supernova remnant "edge on" caught my attention. Are all supernovas expected to explode along a plane, instead of ~uniformly in all directions? Maybe associated with a star's rotation and with most of the force occurring along the equatorial plane?
- Abominable Snowman
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andresgris wrote:The notion of seeing a supernova remnant "edge on" caught my attention. Are all supernovas expected to explode along a plane, instead of ~uniformly in all directions? Maybe associated with a star's rotation and with most of the force occurring along the equatorial plane?
Some supernovas appear to be essentially spherical, while others show various other symmetries (presumably related to spin axis or magnetic axis features).
But I don't think that's what's being suggested here. Supernova remnants tend to fragment into all sorts of complex structure (due to gravity and electromagnetic forces). That happens regardless of the shape of the explosion itself. Here, we have a very evolved (old) remnant, and we're looking at a section that shows regions of planar structure. It probably tells us little or nothing about what this remnant looked like shortly after the supernova that produced it.
"It probably tells us little or nothing about what this remnant looked like shortly after the supernova that produced it."
[quote="APOD Robot"] Pickering's Triangle in the Veil
I have a question regarding the expanding shock wave from Supernovas such as what created the Veil Nebula. Assuming the shock wave expands in a spherical pattern, can anyone tell me how fast that shock wave is moving? And considering how massive these nebula appear, would such an expanding cloud pose a danger to any planetary systems in nearby star systems? NASA is constantly reminding us there is no chance of any fair-sized asteroids impacting the Earth but what are the chances of any nearby stars exploding into a supernova? What would be the danger to our solar system?
- Vacationer at Tralfamadore
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I have a question regarding the expanding shock wave from Supernovas such as what created the Veil Nebula. Assuming the shock wave expands in a spherical pattern, can anyone tell me how fast that shock wave is moving? And considering how massive these nebula appear, would such an expanding cloud pose a danger to any planetary systems in nearby star systems?
The Veil Nebula is traveling at less than 1% the speed of light and should reach the Earth no sooner than 150,000 years.
<<The Veil Nebula is a [~100 light-year wide] cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop (radio source W78, or Sharpless 103), a large but relatively faint supernova remnant. The source [Type II] supernova exploded some 5,000 to 8,000 years ago, and the remnants have since expanded to cover an area roughly 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full moon). Far Ultraviolet Spectroscopic Explorer data supports a distance of about 1,470 light-years.>>
NASA is constantly reminding us there is no chance of any fair-sized asteroids impacting the Earth but what are the chances of any nearby stars exploding into a supernova? What would be the danger to our solar system?
<<On average, a ["dangerously close
"] supernova explosion occurs within 10 parsecs of the Earth every 240 million years. Gamma rays are responsible for most of the adverse effects a supernova can have on a living terrestrial planet
. In Earth's case, gamma rays induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. Phytoplankton and reef communities would be particularly affected, which could severely deplete the base of the marine food chain. In 2009, researchers have found nitrates in ice cores from Antarctica at depths corresponding to the known supernovae of 1006 and 1054 CE, as well as from around 1060 CE. The nitrates were apparently formed from nitrogen oxides created by gamma rays from the supernovae. This technique should be able to detect supernovae going back several thousand years.
Speculation as to the effects of a nearby supernova on Earth often focuses on large stars as Type II supernova candidates. Several prominent stars within a few hundred light years from the Sun are candidates for becoming supernovae in as little as a millennium. In 1996, astronomers at the University of Illinois at Urbana-Champaign theorized that traces of past [Type II] supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata. Subsequently, iron-60 enrichment has been reported in deep-sea rock of the Pacific Ocean by researchers from the Technical University of Munich. 23 atoms of this iron isotope were found in the top 2 cm of crust, and these date from the last 13 million years or so. It is estimated that the supernova must have occurred in the last 5 million years or else it would have had to happen very close to the solar system to account for so much iron-60 still being here. A supernova occurring so close would have probably caused a mass extinction, which didn't happen in that time frame. The quantity of iron seems to indicate that the supernova was less than 30 parsecs away.
Adrian L. Melott et al. estimated that gamma ray bursts from "dangerously close" supernova explosions occur two or more times per billion years, and this has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth.>>